Aron Vincent Salmeri, 27, was arrested for loitering in a public bathroom and violation of parole, Sgt. Lisa Banayat said.
Employees of the store placed Salmeri under citizen's arrest after finding him the bathroom around 2 p.m. at the store at 1900 Santa Rosa Ave., Banayat said.
A Costco employee who went to the restroom saw Salmeri on his hands and knees in a stall and then notified another female employee. Both women saw Salmeri in a stall holding a camera phone and placed him under arrest, Banayat said.